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EP-1734: IGRT for prostate cancer: intrafraction variation analysis and CTV-PTV margin determination
ESTRO 35 2016
S811
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EP-1734 IGRT for prostate cancer: intrafraction variation analysis and CTV-PTV margin determination C. Italia1, R. La Rosa2, P. Della Monica3, S. Masciullo4, O. Ceccarini5, E. Brembilla5, M. Camerlingo4, M. Cardinali5, F. De Osti4, S. Gusmini4, C. Riva4, F. Romeo4 1 Policlinico San Pietro/Policlinico San Marco, Radiotherapy, Ponte San Pietro/Zingonia, Italy 2 Policlinico San Marco, Medical Physics, Zingonia, Italy 3 Policlinico San Pietro, Medical Physics, Ponte San Pietro, Italy 4 Policlinico San Pietro, Radiotherapy, Ponte San Pietro, Italy 5 Policlinico San Marco, Radiotherapy, Zingonia, Italy
Conclusion: We have demonstrated that the γ3%/3mm can be quantitatively estimated from the characteristics of respiratory motion. From the results of multi-regression analysis, reducing the amplitude of respiratory motion would provide high γ3%/3mm. EP-1733 Deep inspiration breath-hold technique using an Arduino P. Gallego1, J. Pérez-Alija1, S. Olivares1, S. Loscos1, E. Ambroa2, A. Pedro1 1 Hospital Plato, Oncología, Barcelona, Spain 2 Hospital General de Cataluña, Radioterapia, Sant Cugat, Spain Purpose or Objective: A large effort has been made in recent years to develop techniques to reduce the dose to normal tissue (especially heart dose) for patients receiving radiation treatment for breast cancer. The deep inspiration breath-hold technique (DIBH) can decrease radiation dose delivered to the heart and this may facilitate the treatment to the internal mammary chain nodes. The aim of this work was both to develop a DIBH method using an Arduino Uno microcontroller board (SmartProyects, Ivrea, Italia) and a simple software to visualize the patient’s level of inspiration. This method provides a cheaper solution to the more expensive commercial ones. Material and Methods: Arduino is an open-source electronics platform based on an easy-to-use hardware and software. We plugged a tri-axial low-g digital acceleration sensor (Bosch's BMA180) to our Arduino board. This accelerometer is then placed on the patient and used as a surrogate to measure the expansion of the patient's thorax during breathing. Even though we chose the gravitational 1g range and our BMA 180 provides a digital full 14 bit output signal, this is still not enough to accurately measure the acceleration changes produced in the patient’s thorax during her breath cycle. We thus measure the orientation change in our BMA180 inside the gravitational field. However, this orientation change is good enough to accurately measure the changes in the patient’s breath cycle. With an In-house developed software programmed in Python 2.7 we are able to visualize these measures and, accordingly, the patient’s breathe cycle. Results: We were able to build a DIBH system using both an Arduino board and an accelerometer. We visualize the patient’s breathe cycle with an In-house software and establish a threshold based on its amplitude. We provide patients with a real-time breathe cycle visualization, so they can have a visual feedback mechanism in order to properly hold their breath when required. Conclusion: Several DIBH methods are commercially available. These methods can decrease the radiation dose delivered to the heart. We have developed an In-house DIBH system with all the functionalities required to implement this technique in our clinic. Building this system is really cheap and amounts to nearly 60 Euros. We are more than happy to freely provide the software needed to implement this method.
Purpose or Objective: 1.to evaluate first set-up accuracy and corrections needed before treatment administration 2.to assess intrafraction variability 3.to determine CTV-PTV margins according to intrafraction uncertainties Material and Methods: Forty-five consecutive prostate cancer patients, undergoing radical or postoperative imageguided radiation therapy with or without gold seed implant in a newly opened department, were considered. On each session a first set of portal images was obtained at 0° and 90° degrees, using a low-dose MV imager. Positioning errors were measured in the three directions and corrected if > 1 mm. After treatment a second set of images was daily produced and displacements measured. Comparison between before-treatment images and planning DRRs represents setup accuracy. Comparison between end-of-treatment images and planning DRRs shows intrafraction variability Systematic and random errors were analysed and incorporated in the Van Herk formula (2.5 ∙ Σ+ 0.7∙ σ), to determine ideal CTV-PTV margins. Results: All patiens were suitable for the analysis. Results are summarized in the table.
A total of 6632 images were analysed. Mean errors were <1 mm for all measurements. In intrafraction shift analysis systematic errors were <1 mm, random errors were <2 mm and calculated CTV-PTV margins ranged from 1.7 to 2.7 mm. Conclusion: Good accuracy and precision for first positioning procedures were found. If hypothetically IGRT were omitted and CTV-PTV margins were based on first set-up errors only, margins ranging from 6.3 to 8.4 mm in the various directions would be mandatory. On the contrary, according to the policy of our department, with the use of daily IGRT and based on our excellent results of intrafraction variation analysis, CTV-PTV margins can be limited to 2.2, 2.7 and 1.7 mm, respectively in lateral, anteroposterior and craniocaudal direction. EP-1735 Impact of respiratory motion on breast tangential radiotherapy using the field-in-field technique H. Tanaka1, T. Yamaguchi1, M. Kawaguchi1, S. Okada1, Y. Kajiura1, M. Matsuo1 1 Gifu University, Radiology, Gifu, Japan Purpose or Objective: The field-in-field (FIF) technique has become a widely performed method of administering tangential whole breast radiotherapy. However, as the FIF technique requires the precise setting of the position of the multi-leaf collimators (MLCs) in order to reduce hot spots, there is concern that its use could significantly change the dose distribution to the target volume due to respiratory
S811
________________________________________________________________________________
EP-1734 IGRT for prostate cancer: intrafraction variation analysis and CTV-PTV margin determination C. Italia1, R. La Rosa2, P. Della Monica3, S. Masciullo4, O. Ceccarini5, E. Brembilla5, M. Camerlingo4, M. Cardinali5, F. De Osti4, S. Gusmini4, C. Riva4, F. Romeo4 1 Policlinico San Pietro/Policlinico San Marco, Radiotherapy, Ponte San Pietro/Zingonia, Italy 2 Policlinico San Marco, Medical Physics, Zingonia, Italy 3 Policlinico San Pietro, Medical Physics, Ponte San Pietro, Italy 4 Policlinico San Pietro, Radiotherapy, Ponte San Pietro, Italy 5 Policlinico San Marco, Radiotherapy, Zingonia, Italy
Conclusion: We have demonstrated that the γ3%/3mm can be quantitatively estimated from the characteristics of respiratory motion. From the results of multi-regression analysis, reducing the amplitude of respiratory motion would provide high γ3%/3mm. EP-1733 Deep inspiration breath-hold technique using an Arduino P. Gallego1, J. Pérez-Alija1, S. Olivares1, S. Loscos1, E. Ambroa2, A. Pedro1 1 Hospital Plato, Oncología, Barcelona, Spain 2 Hospital General de Cataluña, Radioterapia, Sant Cugat, Spain Purpose or Objective: A large effort has been made in recent years to develop techniques to reduce the dose to normal tissue (especially heart dose) for patients receiving radiation treatment for breast cancer. The deep inspiration breath-hold technique (DIBH) can decrease radiation dose delivered to the heart and this may facilitate the treatment to the internal mammary chain nodes. The aim of this work was both to develop a DIBH method using an Arduino Uno microcontroller board (SmartProyects, Ivrea, Italia) and a simple software to visualize the patient’s level of inspiration. This method provides a cheaper solution to the more expensive commercial ones. Material and Methods: Arduino is an open-source electronics platform based on an easy-to-use hardware and software. We plugged a tri-axial low-g digital acceleration sensor (Bosch's BMA180) to our Arduino board. This accelerometer is then placed on the patient and used as a surrogate to measure the expansion of the patient's thorax during breathing. Even though we chose the gravitational 1g range and our BMA 180 provides a digital full 14 bit output signal, this is still not enough to accurately measure the acceleration changes produced in the patient’s thorax during her breath cycle. We thus measure the orientation change in our BMA180 inside the gravitational field. However, this orientation change is good enough to accurately measure the changes in the patient’s breath cycle. With an In-house developed software programmed in Python 2.7 we are able to visualize these measures and, accordingly, the patient’s breathe cycle. Results: We were able to build a DIBH system using both an Arduino board and an accelerometer. We visualize the patient’s breathe cycle with an In-house software and establish a threshold based on its amplitude. We provide patients with a real-time breathe cycle visualization, so they can have a visual feedback mechanism in order to properly hold their breath when required. Conclusion: Several DIBH methods are commercially available. These methods can decrease the radiation dose delivered to the heart. We have developed an In-house DIBH system with all the functionalities required to implement this technique in our clinic. Building this system is really cheap and amounts to nearly 60 Euros. We are more than happy to freely provide the software needed to implement this method.
Purpose or Objective: 1.to evaluate first set-up accuracy and corrections needed before treatment administration 2.to assess intrafraction variability 3.to determine CTV-PTV margins according to intrafraction uncertainties Material and Methods: Forty-five consecutive prostate cancer patients, undergoing radical or postoperative imageguided radiation therapy with or without gold seed implant in a newly opened department, were considered. On each session a first set of portal images was obtained at 0° and 90° degrees, using a low-dose MV imager. Positioning errors were measured in the three directions and corrected if > 1 mm. After treatment a second set of images was daily produced and displacements measured. Comparison between before-treatment images and planning DRRs represents setup accuracy. Comparison between end-of-treatment images and planning DRRs shows intrafraction variability Systematic and random errors were analysed and incorporated in the Van Herk formula (2.5 ∙ Σ+ 0.7∙ σ), to determine ideal CTV-PTV margins. Results: All patiens were suitable for the analysis. Results are summarized in the table.
A total of 6632 images were analysed. Mean errors were <1 mm for all measurements. In intrafraction shift analysis systematic errors were <1 mm, random errors were <2 mm and calculated CTV-PTV margins ranged from 1.7 to 2.7 mm. Conclusion: Good accuracy and precision for first positioning procedures were found. If hypothetically IGRT were omitted and CTV-PTV margins were based on first set-up errors only, margins ranging from 6.3 to 8.4 mm in the various directions would be mandatory. On the contrary, according to the policy of our department, with the use of daily IGRT and based on our excellent results of intrafraction variation analysis, CTV-PTV margins can be limited to 2.2, 2.7 and 1.7 mm, respectively in lateral, anteroposterior and craniocaudal direction. EP-1735 Impact of respiratory motion on breast tangential radiotherapy using the field-in-field technique H. Tanaka1, T. Yamaguchi1, M. Kawaguchi1, S. Okada1, Y. Kajiura1, M. Matsuo1 1 Gifu University, Radiology, Gifu, Japan Purpose or Objective: The field-in-field (FIF) technique has become a widely performed method of administering tangential whole breast radiotherapy. However, as the FIF technique requires the precise setting of the position of the multi-leaf collimators (MLCs) in order to reduce hot spots, there is concern that its use could significantly change the dose distribution to the target volume due to respiratory